An integral part of studying the complex
atmosphere is using computer models where the chemistry and dynamics are simulated by mathematical equations. You can look at a cloud and say,
How can I describe what its doing quantitatively? I
cant! The system is far too complicated. But should I give up? No! I
can simplify the system so that its tractable mathematically, says Daniel
Jacob, at Harvard University. Then I can run the model and compare the results
with what I see nature doing. In places where scientists see that the model and nature arent the same, they can work to understand the chemistry better.

When we see differences between our models and data from actual observations
in the field or from satellites, were not happy, explains Guy Brasseur, a
modeling expert at the Max Planck Institute for Meteorology and the National
Center for Atmospheric Research. But we often learn about a process
thats new to us that way.

Models are a means of testing our understanding, so that we can make
predictions, continues Brasseur. Now our understanding of the atmosphere is
developed in a partnership between observations, work in the lab, and
modeling.

Satellite observations are producing large amounts of data and are changing
the way atmospheric chemistry is done. I think this is a fantastic time for
young people to enter the field of atmospheric chemistry because our field is
undergoing a revolution, adds Jacob. My community is having to think about
satellite observations. Interpreting satellite observations is a very difficult
task. Satellite sensors observe the Earth through most of the atmosphere, and
the data we want are in small quantities buried in the noise of other data.
But we need to understand what satellite observations are saying to us, because
we need that global scale [perspective].

A global systems approach is prominent in Brasseurs mind. More and
more, weve learned that we cannot look at the atmosphere in isolation from
the rest of the Earth, he says. We must see it in the context of its
interactions with the oceans, the biosphere, and human activities—with the whole
Earth as a system. We must be developing global, comprehensive, integrated
Earth system science models.

Daniel Jacob explains, Now we have global three-dimensional models.
Were not yet ready to put together the biosphere and the atmosphere and
economics, but there are people who are dreaming about this.